Extreme ultraviolet interference lithographic exposure tool was installed at the long undulator beamline in NewSUBARU for the resist evaluation in 25 nm node and below. It was confirmed that the spatial coherence length is 1.1 mm using a 10-μm-wide slit in the Young's double slit experiment. The transmission grating was the key component to decide the resist pattern size and contrast for EUVIL. To obtain the high contrast of the interference fringes of the two window transmission grating on the wafer, the transmission grating was designed. The window size of the transmission grating optimized to be 300X30 μm2 in size to avoid Fresnel diffraction which reduces the contrast of the interference fringes on the wafer. In addition, to obtain highest diffraction efficiency, TaN employed as the absorber material, and the thickness of the absorber was optimized to be 70 nm. Furthermore "Center stop" layer was design to reduce the transmitted light from the region between two diffraction grating windows to obtain high contrast of the interference fringes on the wafer. A 25-nm half pitch (hp) resist pattern was successfully replicated by extreme ultraviolet interference lithography (EUV-IL) utilizing a two-window transmission grating pattern of a 50-nm line and space (L/S). As results, the transmission grating design can be applied for the resist patterning of 25 nm and below in EUV-IL.
2010 The Society of Photopolymer Science and Technology (SPST)